OF THE ROGER N. CLARK

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--- --- MI08 (NGC 3556), GALAXY IN URSA MAJOR R.A. llh 1l.6m, Dec. 55° 41 ' (2 000.0) Technical. M 1 08 is a nearly edge-on spiral galaxy of type Sc. First discovered by Pierre Mechain in 1781, it was not commonly included in Messier's catalog until the early 1970s. M I 08 is about 25 million light-years away and has many obscuring dust lanes and no pronounced central bulge. VISUAL ASTRONOMY OF THE DEEP SKY Visual. MI08 appears 7.8 by 1.4 arcminutes in angular size, with a total bright_ ness of magnitude 10.8 and a mean surface brightness of22.0 magnitudes per square arcsecond. It is 48 arc-minutes northwest of the Owl Nebula, M97 (NGC 3587). Through the 8-inch under moderate skies, no detail corres_ ponding to dark lanes was seen. The nucleus looked like a star, and an actual star is superimposed on the galaxy's western side. The galaxy appeared as a uniform, elongated glow, fading at the edges into the sky background. M97 (NGC 3587) THE OWL NEBULA: PLANETARY NEBULA IN URSA MAJOR R.A. llh 14.9m, Dec. 55° 02 ' (2000.0) Technical. M97 was discovered by Charles Messier's compatriot Pierre Mechain in 1781. When William Parsons, Lord Rosse, observed it with his 72-inch speculum-metal reflector in 1848, he made a drawing remarkably like an owl's face, and M97 has been the Owl Nebula ever since. It is thought to be about 1600 light-years distant and about 1.5 light-years in diameter. Its gas is only 1/10 to 1/100 as dense as that of a typical planetary nebula, suggesting that M97 is relatively old and has been expanding and thinning for a long time. The 14th-magnitude central star has an effective temperature of 85 000 kelvin. A VISUAL ATLAS OF DEEP-SKY OBJECTS Visual. The two dark "owl's eyes" are hard to detect in small to medium telescopes. With a diameter of 2.5 arc-minutes and a total magnitude of 11.0, the nebula has a mean surface brightness of 22.6 magnitudes per square arc-second - very low for a planetary nebula. By comparison, the famous Ring Nebula, M57 in Lyra, has a mean surface brightness of 17.9 magnitudes per square arcsecond. With the 8-inch under moderate to good skies, the eyes were barely seen. If I had not known of their existence I probably would not have detected them at all. When making the drawing I did not know the eyes' true orientation, so the fact that they are placed correctly indicates that they really were seen - unless blind luck was at work. This uncertainty shows the extreme difficulty in observing the owl's eyes. Better skies or a larger telescope are needed . • ---5' --- Photograph of MI08. South is up . (Courtesy Evered Kreimer, The Messier Album.) Drawing of MI08. Scale: 1.2 arc-min/cm 8-inch flll.5 Cassegrain 20mm Erfle (117X) 12.4mm Erfle (188X, best view) 7mm Erfle (334x) Viewing Distance 25 X:115 200x:14 50 X: 57 300 X : 10 100 X : 29 400X: 7 air mass: 1.41, faintest star: 13.8 at zenith, 188X; no tracking 5/ 1 5/83 8:41-8:52 UT at Barbers Point, Hawaii; R. Clark • -- 5' --- Photograph of M97. South is up. (Courtesy Evered Kreimer, The Messier Album.) Drawing of M97. Scale: 1.2 arc-min/cm 8-inch fI 1 1.5 Cassegrain 20mm Erfle (117x) 12.4mm Erfle (l88x, best view) Viewing Distance (cm) 25 X:115 200 X:46 50 X: 57 300 X : 10 100x: 29 400 X: 7 air mass: 1.36, faintest star: 13.8 at zenith, 188x; no tracking 5/ 1 5/83 8:25-8:40 UT at Barbers Point ' Hawaii' , R. Clark 132 133
-- VISUAL ASTRONOMY OF THE DEEP SKY M66 (NGC 3627) NGC 3628, M65 (NGC 3623), M65: M66: GALAXIES IN LEO A VISUAL ATLAS OF DEEP-SKY OBJECTS R.A. llh 18.9m, Dec. 13° 07' R.A. llh 20.2m, Dec. 13° 01 ' NGC 3628: R.A. llh 20.3m, Dec. 13° 37' (2 000.0) Technical. This tṛio of galaxies fits into a I w_powei field of vIew. They are members of te Leo Cluster of Galaxies, about 30 million light-years away, which also includes M95, M96 and M 105. AIl three galaxies are type-Sb spirals, with NGC 3628 being nearly edge-on. M66 has thick spiral arms and dust lanes. M65 appears like a miniature Andromeda Galaxy (M31); it has a dark dust lane on the east side, and the spiral arms . are wound much like M31 s. M66 has a dIameter of 50 000 light-years; M65 60 000 light-years; and NGC 3628, about 90 000 light-years. Visual. M65 and M66 can be detected in binoculars, while NGC 3628 requires a small telescope under good skies. M66 has a total magnitude of 9.7 and an angular size of 8.0 by 2.5 arc-minutes, yielding a mean surface brightness of2l.6 magnitudes per square arcsecond. M65 has a total magnitude of 10.3, a size of 7.8 by l.6 arc-minutes; and a mean surface brightness essentially the same, 2l. 7. NGC 3628 is more difficult, with a total magnitude of 10.3 and a size of 12 by 2 arcminutes, yielding a fainter mean surface brightness, 22.4 magnitudes per square arcsecond. In the 8-inch, M66 shows an oval central region surrounded by the oval glow of the fainter spiral arms. The arms appear dimmer than the impression given by most photographs, no doubt because the central region is usually overexposed. The oval corresponding to the arms is oriented generally north - south, while that of the bright central region is more northwest - southeast. The southern arm looked pointed, an appearance familiar from photographs. M65 showed a bright central region surrounded by the fainter spiral arms. The dark lane could not be seen in the 8-inch. NGC 3628 appeared considerably fainter than either M65 or M66 and was only slightly brighter in the center. The spiral arms faded gradually into the sky background, and no dark lanes could be seen during this observation. However, under excellent skies the dark lane so evident in the photograph is visible in an 8-inch telescope. 134 135
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OF THE ROGER N. CLARK
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Published by Sky Publishing Corpora
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CONTENTS M78 (NGC 2068) NGC 207 1,
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PREFACE During research for this bo
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VISUAL ASTRONOMY OF THE DEEP SKY AB
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VISUAL ASTRONOMY OF THE DEEP SKY TH
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.. .. .. .. VISUAL ASTRONOMY OF THE
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e viewed with enough magnification
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lens and a piano-convex eye lens. A
Page 23 and 24: VISUAL ASTRONOMY OF THE DEEP SKY TH
Page 25 and 26: controlled depends on how many laye
Page 27 and 28: The Lumicon H-Beta Filter (Figure 3
Page 29 and 30: every 1 ° in declination and 4 min
Page 31 and 32: error of only one quarter the field
Page 33 and 34: Table 4.1. Ideal limiting magnitude
Page 35 and 36: 5 Making drawings and keeping recor
Page 37 and 38: more detail in the future. They add
Page 39 and 40: .. .. .. ... Contrast (C) C Log(C)
Page 41 and 42: VISUAL ASTRONOMY OF THE DEEP SKY A
Page 47 and 48: --- VISUAL ASTRONOMY OF THE DEEP SK
Page 49 and 50: --- M76 (NGC 650-651), PLANETARY NE
Page 53 and 54: -- -- M45, THE PLEIADES OPEN CLUSTE
Page 55 and 56: -- Brightest stars of the Pleiades
Page 57 and 58: M42 (NGC 1976), M43 (NGC 1982), THE
Page 59 and 60: --- --- --- VISUAL ASTRONOMY OF THE
Page 61 and 62: -- --- NGC 2023 NGC 2024, IC 434 (T
Page 63 and 64: --- --- M78 (NGC 2068), NGC 2071, D
Page 65 and 66: VISUAL ASTRONOMY OF THE DEEP SKY --
Page 67 and 68: --- M67 (NGC 2682), OPEN CLUSTER IN
Page 69 and 70: -- VISUAL ASTRONOMY OF THE DEEP SKY
Page 71 and 72: --- -- M82 (NGC 3034), PECULIAR GAL
Page 73: -- --- --- MI05 (NGe 3379) NGe 3384
Page 77 and 78: MI09 (NGe 3992), GALAXY IN URSA MAJ
Page 79 and 80: -- --- M99 (NGC 4254), GALAXY IN CO
Page 81 and 82: == -- VISUAL ASTRONOMY OF THE DEEP
Page 83 and 84: --- --- -- NGC 4449, GALAXY IN CANE
Page 85 and 86: -- -- --- VISUAL ASTRONOMY OF THE D
Page 87 and 88: --- -- M90 (NGC 4569), GALAXY IN VI
Page 89 and 90: --- -- M94 (NGC 4736), GALAXY IN CA
Page 93 and 94: -- VISUAL ASTRON0MY OF THE DEEP SKY
Page 95 and 96: -- --- -- VISUAL ASTRONOMY OF THE D
Page 97 and 98: -- -- VISUAL ASTRONOMY OF THE DEEP
Page 99 and 100: --- -- M83 (NGC 5236), GALAXY IN HY
Page 107 and 108: --- VISUAL ASTRONOMY OF THE DEEP SK
Page 109 and 110: --- -- VISUAL ASTRONOMY OF THE DEEP
Page 111 and 112: ---------------- 5 / --------______
Page 113 and 114: --- -- VISUAL ASTRONOMY OF THE DEEP
Page 115 and 116: VISUAL ASTRONOMY OF THE DEEP SKY --
Page 119 and 120: -- -- VISUAL ASTRONOMY OF THE DEEP
Page 123 and 124: -- MI5 (NGC 7078), GLOBULAR CLUSTER
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VISUAL ASTRONOMY OF THE DEEP SKY A
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--- VISUAL ASTRONOMY OF THE DEEP SK
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VISUAL ASTRONOMY OF THE DEEP SKY A
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-- VISUAL ASTRONOMY OF THE DEEP SKY
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-- ·rl E I u L ro 5 +J Q) (f) 0 Y
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-- --- VISUAL ASTRONOMY OF THE DEEP
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VISUAL ASTRONOMY OF THE DEEP SKY NG
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'2 5 -rl E I U L CO '---' -t-J ill
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VISUAL ASTRONOMY OF THE DEEP SKY AP
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VISUAL ASTRONOMY OF THE DEEP SKY Ta
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-- Appendix E A catalog of deep-sky
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--- -- VISUAL ASTRONOMY OF THE DEEP
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-- -- --- VISUAL ASTRONOMY OF THE D
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--- --- VISUAL ASTRONOMY OF THE DEE
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-- -- VISUAL ASTRONOMY OF THE DEEP
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-- APPENDIX F: OPTIMUM DETECTION MA
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------- VISUAL ASTRONOMY OF THE DEE
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--- VISUAL ASTRONOMY OF THE DEEP SK
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VISUAL ASTRONOMY OF THE DEEP SKY -
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VISUAL ASTRONOMY OF THE DEEP SKY -
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G VISUAL ASTRONOMY OF THE DEEP SKY
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INDEX INDEX M70 (NGC 6681), 312, 31
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OF THE ROGER N. CLARK

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